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Figure 1. System bars, including the [1] status
bar, and [2] navigation bar.

The
system bars are screen areas dedicated to the display of notifications, communication
of device status, and device navigation. Typically the system bars (which consist of the status
and navigation bars, as shown in figure 1) are displayed
concurrently with your app. Apps that display immersive content, such as movies or images,
can temporarily dim the system bar icons for a less distracting experience,
or temporarily hide the bars for a fully immersive experience.

If you're familiar with the Android Design
Guide, you know the importance of designing your apps to conform to standard Android UI
guidelines and usage patterns. You should carefully consider your users'
needs and expectations before modifying the system bars, since they give users a
standard way of navigating a device and viewing its status.

This class describes how to dim or hide system bars across different versions of Android
to create an immersive user experience, while still preserving easy access to the system
bars.